'Hit it at speed and they could be across before the orbitals got a solution.'

'Without vehicles? Would you risk it?'

Selaton considers the question for a moment before answering. 'Theoretical if I was trapped on an enemy world with no immediate prospect of reinforcements, I'd want to link up with friendly forces as quickly as possible.'

'Practical the railhead terminal offers cover,' says Ventanus, gesturing to the building's shell-cratered roof. The covering is still largely intact, though shafts of wounded blue light spear through its smoke-fogged interior. 'Server Tawren's auspex feeds suggest that whoever's leading this force is cautious. He's moving from cover to cover, taking his time.'

'But she lost them,' points out Selaton. 'We don't know where they are now.'

'If he wants to reach Foedral Fell alive, he'll come this way,' asserts Ventanus.

'Did the Server happen to mention anything about their numbers?'

'At least five hundred, maybe more,' replies Ventanus.

'Then I hope you're right,' says Selaton with relish.

IV.

They come in ragged squads at first. Tentatively, like thieves in the darkness.

Emerging from the gutted shell of a Titan repair facility, two groups of Word Bearers emerge like wary grazing beasts approaching a watering hole frequented by an apex predator. They move swiftly between the burning hulks of derailed shipping containers. Ventanus lets a finger slip beneath the trigger guard of his bolter.

He lets out a breath.

These are just scouting forces probing thrusts into the flaming ruins at the edge of the terminus. They hope to provoke any potential ambushers into carelessness, but Ventanus has been specific in his orders. None of his warriors open fire, though each of them dearly wishes to. If this trap is to be sprung completely, then the Word Bearers must fully stick their heads into the noose.

Watching the enemy warriors, Ventanus sees the plate of their legionary armour has changed again. First it changed from granite grey to crimson. Now it is a mixture of scorched black, bare-metal iron and a few remaining patches of bruised blood. The first was a choice, but this latest change is not. The light of Calth's wounded star has robbed the XVII Legion of uniformity, and Ventanus realises he can no longer think of them as legionaries.

They are too ragged, too individual to be worthy of such a unifying term.

They do not even deserve any force designation such as company or battalion.

This is a warband, a haphazard arrangement of survivors.

Within the protective environment of his helmet, his lip curls in contempt.

You won't be survivors for much longer.

These forward elements of the Word Bearers advance into the railhead terminal, still moving cautiously, still keeping one eye on the sky and the unseen orbital weapons. They pass out of sight, obscured by the banks of smoke, and Ventanus counts the long seconds in time with his heartbeat.

He wonders if he has made a mistake. Perhaps the Word Bearers have split into smaller groups, each one making its own way to Foedral Fell. He senses Selaton's scrutiny, but keeps his gaze fastened on the buckled tracks leading to the terminus. He wills the enemy to show itself.

Then the real prize comes into view.

A marching column of Word Bearers emerges from the shelter of the repair facility, moving with as much speed as caution allows. Ventanus calculates their numbers to be close to six hundred. All infantry no vehicle support and no Dreadnoughts. A few light artillery pieces, but nothing that gives him pause or second thoughts.

But it is more than their lack of heavy firepower that convinces him that this attack will work. Watching the exaggerated caution in their movements, Ventanus realises that the Word Bearers are in a state of shock. They came to Calth arrogant, confident of total victory. They forgot who they were fighting. That slip allowed the Ultramarines to deliver a stinging reprimand, the gut-punch from a downed fighter that turns the bout on its head.

Ventanus waits until he is sure that there are no more Word Bearers yet to emerge from hiding.

He rises to his feet and reaches behind him, hand outstretched.

Another sergeant, Barkha, hands Ventanus the standard, its haft dented and the fabric of the company colours torn and ragged. He plants it at the edge of the ridge and pulls his bolter tight to his shoulder.

'For Calth!' he shouts, and two hundred warriors of the Fourth rise up.

Bolter fire blitzes down into the wreckage in front of the railhead terminus. The barking volley punches scores of Word Bearers from their feet before they are even aware that they are under attack. A second volley kills dozens more. Now the enemy are moving into cover, returning fire and keeping their heads down. The Ultramarines do not advance, but hold their position, pouring fire into the enemy ranks. Ventanus is a keen-eyed shot and takes his time, picking his targets with care. He scans for officers and sergeants among the Word Bearers. His task is made more difficult by the fact that the scorching of their war-plate has obliterated most symbols of rank.

In lieu of conventional markings, he targets those with the greatest disfigurements wrought upon their shoulder guards or helmets, the most heavily scarred or those to whom others appear to defer. He puts a mass-reactive through the helm of a warrior whose breastplate is hung with dagger-like fetishes and whose mail cloak glitters with an oily sheen. He kills another with a jagged star symbol cut into the faceplate of his helm. A warrior with a long chain-glaive and a crackling power claw dies with his chest blown out as he runs between two broken tenders. Any one of these kills would earn him a commendation for marksmanship, had anyone but him seen the shots.

Ventanus feels the same rightness to these kills he felt as they first fought their way into Lanshear. At this moment, his bolter is more than just a weapon, it is an instrument of just retribution, the nemesis of all that is faithless and treacherous. He ejects his emptied magazine and slots a fresh one home with smooth ease.

A series of explosions bloom along the ridge-line, and the impacts hurl perhaps twenty Ultramarines to the ground. Ventanus recognises the detonations of lightweight field artillery shells. Scavenged Army weapons, not Legion ordnance. All the downed Ultramarines are quickly back on their feet and firing downhill with only a fractional pause in their killing.

The Word Bearers are shooting back, but their response is desultory at best. Some enemy warriors are not even bothering to return fire, and it takes Ventanus a moment to realise why. Selaton reaches the same conclusion a moment later.

'They don't have enough ammunition to fight back,' he says.

That same realisation is spreading amongst his warriors, and Ventanus feels their desire to take the fight to the Word Bearers. They want to look the traitors in the eye as they kill them. They want to spill enemy blood with their own two hands. Like them, Ventanus wants to mag-lock his bolter and advance with his sword drawn, to teach Lorgar's faithless sons the cost of not finishing the job they started.

He checks the thought.

The theoretical is glorious, but this practical does not allow for emotion.

'Hold position,' he says. 'Maintain fire.'

The tone of his voice is unequivocal and locks the Ultramarines in place.

The Word Bearers are no longer shooting back. Instead, they are risking the relentless fire of the Ultramarines as they run for the rail terminus. They have abandoned the field guns, knowing they are useless against warriors protected by power armour.

Dozens of Word Bearers are cut down as they cross the open ground, but hundreds more survive to reach the smoke-choked cover of the terminal. Thick smoke swallows them and not even Ventanus's auto-senses can penetrate the chem-rich blackness.

Selaton looks at him, waiting for him to give the order.

Word Bearers bodies litter the ground.

Some will still be alive, and Ventanus is glad. They will know what is coming.

He opens a vox-link on a pre-arranged frequency.

'Server Tawren, this is Ventanus. The enemy is in the kill-box,' he says. 'You have a solution?'

'Affirmative,' comes Tawren's vox-distorted reply. 'Engaging now.'

Her voice is without accent and apparently devoid of emotion though Ventanus knows her well enough to know that is not true. He has come to like her, as much as any post-human can be said to like a chimeric, fully modified adept of the Martian priesthood.

Selaton hears this exchange and turns his gaze upon the railhead terminus as the clouds light up with the approaching storm. A dazzling tower of light flashes from space, briefly linking an orbital lance battery with the surface of Calth. The shell-punctured roof of the terminal lifts off in a rush of explosive kinetic force before vanishing in a cloud of fire.

Ventanus does not flinch as the electromagnetic pulse and colossal overpressure wash over him. With one hand on the company standard, he stands immobile as another lance strike pounds the railhead terminus, then another. Twice more the orbital battery unleashes its power, and when the roiling banks of volcanic smoke are blown clear, nothing remains.

The ground has been vitrified. Not so much as a single brick or nub of steelwork remains standing within a five-hundred-metre radius of the first impact point.

Ventanus nods in satisfaction and returns the standard to Sergeant Barkha.

He pre-empts Selaton's question of the lance strike's timing before it is asked.

'Because I want the last sight of every Word Bearer to be an Ultramarine,' says Ventanus.

V.

The caves sit beneath a conurb-ring on the southern transit hub of the Uranik Radial, a once populous region of vast habitation blocks a hundred kilometres west of Lanshear. Its hyperstructures and sprawling mega-towers were toppled by the guns of warring Titans, in a firestorm like the coming of an apocalypse. Heedless of the terrified inhabitants, traitor engines and loyalist forces duelled in a battle that left hundreds of thousands of combatants dead, but saw no real victor as each side's forces were drawn away to higher-value objectives.

The caves are a marvel, a series of naturally occurring subterranean voids that local legends attribute to the mythical serpent said to have honeycombed the bedrock of Calth in the planet's prehistory. No one believes such things, not even children, but a new serpent has made its lair in the coiling tunnels beneath the Uranik Radial.

His name is Hol Beloth, and once he commanded an army of annihilation, a genocidal host that sought not to conquer and enslave but to destroy in the name of Horus. Half a million warriors rallied to his banner.

The barest fraction of that force remains.

His army has been reduced to less than ten thousand, and even this number is largely made up of the mangy rabble of the brotherhoods: among them the Kaul Mandori, the Tzenvar Kaul, the Jeharwanate, and the Ushmetar Kaul. Bloodied and humbled, the predatory hosts of Hol Beloth take refuge in the Uranik arcology, invisible to the murderous fire of the orbital batteries and sheltered from the deadly radiation scouring the surface, but tarred with failure.

As falls from grace go, Hol Beloth's is all but complete.

Hol Beloth is one of the anointed ones, a warlord of vaunted ambition and proven battle-worth. He has led conquests on a thousand worlds, seen the fall of empires and brought ruin to uncounted enemies. He is all this and more, but he fears that his dream of ascending to stand at the side of Lord Aurelian is slipping from his grasp.

He still does not understand how they failed.

The Ultramarines were broken, scattered and leaderless. Within minutes of destruction.

And then the heavens rained fire and killing light, gutting Titans with every hammerblow from orbit and reducing entire warhosts to ash. Somehow, the enemy had regained control of the orbital batteries and turned what should have been his greatest triumph into his blackest defeat. Lanshear was to burn in the thunder of Hol Beloth's guns, but the storm turned and tore the beating heart from his chest.

He broods in a cave that echoes with the heartbeat of the dying world, with nothing but ashes for companionship. At his full height, Hol Beloth is a towering giant in crimson armour, his flesh cut with the words of Lorgar and inked in consecrated blood, but defeat has bowed him. He was chosen for great things, but failed to live up to his end of that bargain, and the forces that empowered him have forsaken his ambitions.

For all Hol Beloth knows, his army may be the last alive on Calth.

His fellow commanders. Do any of them yet live?

Is Kor Phaeron dead or does he still fight to bring the Word to Calth?

Hol Beloth has no answers and the sense of loss is paralysing him.

The warp-flask sits beside him, the oil-dark liquid stagnant and lifeless, where once it wriggled and slithered with the motion of something foetal and immeasurably ancient. He speaks to it, hoping to hear from his fellow commanders, but receives no reply. The thing that deigned to squeeze a fragment of its consciousness into that many-angled space is gone, and Hol Beloth has never felt more isolated. The Ultramarines control the few remaining satellites, and rad-storms on the surface make a mockery of any attempt at encrypted vox.

He looks up as he hears approaching footsteps, legionary footsteps. His mouth curls in a sneer as he sees Maloq Kartho. The Dark Apostle filled his head with visions of power and majesty throughout the approach to Calth and their campaign of extermination. Like all true zealots, he refuses to let their utter defeat diminish his passion. Hol Beloth wants to kill him, but when the nights come to Calth the muttering shadows still attend the Apostle like unseen flunkies.

And in the caverns beneath Calth, it is always night.

'What do you want?' demands Hol Beloth.

'To take the Word to the Ultramarines,' says Kartho. 'As you should.'

'You want to fight?' snaps Hol Beloth. 'Go ahead. Make your way to the surface and see how long it takes the orbital guns to end you.'

Kartho is a bleak presence similarly marked, but thrice favoured. He has the blessing of the primarch, the empyrean and the beasts from beyond the veil. His armour glistens, as though freshly daubed with blood, and the runic inscriptions carved into every plate writhe in the azure bioluminescence of the cave. His helm bears a single horn at his right temple that curls around his head to an iron-sheathed point at his left cheek. At his back is a long staff, black-hafted and trailing smoky shadows that etch themselves upon the air.

His face is angular, swathed in darkness and hard to read.

Hol Beloth suspects this to be deliberate artifice on Kartho's part.

'You think your work on Calth is done, Beloth?' says the Dark Apostle. 'Do you really believe your task was simply to fight a mortal war? The Warmaster and Lorgar Aurelian require you to do more than spill blood with bolt and blade. They require you to transform the canvas of the galaxy, to bring great truths to those who have been blinded by the Emperor's empty promises. You are an avatar of the new age.'

Anger touches Hol Beloth and he rises from his torpor with one hand hovering near the hilt of his war-blade, the other curled in a fist.

'You spoke those words before,' he says. 'When I marched at the head of an unstoppable army. They put fire into the hearts of all who heard them, but I understand their truth now. They are as hollow as a Colchisian promise and just as meaningless.'

Maloq Kartho unhooks the spiked staff from his back, and Hol Beloth thinks for a moment he means to attack him. Instead, Kartho plants it into the ground and the muttering shadows swell at his back. The staff's length is scrimshawed with catechisms and blessings copied from Lorgar's great book and topped with a circular finial, the eight spines of the Octed radiating from its centre.

'You are weak, Hol Beloth,' says the Dark Apostle. 'Weak and stupid. A petulant child who weeps and wails and gnashes his teeth the first instant his desires are thwarted.'

Hol Beloth reaches for his sword, but before the blade is even half drawn, the dark smoke around Kartho's staff whips out to slap his hand from the hilt. Kartho is in front of him an instant later, moving without seeming to move, as though the muttering shadows have borne him aloft.

Hol Beloth takes a backward step, surrounded by a veil of darkness that ripples with undulant motion, like a slick of oil in the air. Shapes move within its depths, infinitesimal fragments of immense presences from beyond space and time, pressing at the meniscus that separates this reality from theirs. They have no form, save that which he imprints upon them; a multitude of eyes, fanged mouths and curving horns that manifest and fade as soon as he looks.

They are hungry. They feel the beat of his heart and crave the taste of his lifeblood.

He is powerless to stop them if they attack.

Kartho steps in close, and the darkness parts before him. It wraps itself around him like a shroud, slithering over the curved surfaces of his war-plate, its lightless form lingering at his back like an acolyte.

The sight disgusts Hol Beloth.

'To think I anointed you and set your feet upon the path to glory,' says the Dark Apostle with a disappointed shake of his head. 'Lorgar brought us truth from the place where gods and mortals meet, but you do not see it. You are too ignorant to see it. You have a chance to leave your mortal shell behind and rise to glory, but your moment is passing with every second you spend in wretched self-pity.'

Hol Beloth does not fully understand Kartho's words, but he feels the terror of everything he was promised slipping beyond his reach, never to come again. He drops to one knee before the Dark Apostle, head bowed as a supplicant.

'Tell me what I must do,' he says.

The notion of submitting to the Dark Apostle's designs is abhorrent to him, but now he knows he will say or do anything to hold on to his ambitions. So badly does he desire to stand at the side of Lorgar and Horus that he willingly begs for Kartho's scraps.

'The galaxy is changing, Hol Beloth,' says the Dark Apostle. 'The old ways are passing, and a new order is establishing itself. What was is no more, and what will be is just taking shape. Those who embrace that truth will prosper. Those who do not will perish.'

'Tell me what I must do,' he asks again. 'What do the powers require of me?'

Kartho leans down and his hooded eyes are alight with a passion only bloodshed ignites.

'Atrocity,' says Kartho. 'They require atrocity.'

VI.